N-isopropyl chitosan. A pH- and thermo-responsive polysaccharide for gel formation

[Display omitted] •Chitosan was modified with isopropyl side chains on the amino groups.•N-isopropyl chitosan shows altered hydrophobic/hydrophilic features.•N-isopropyl chitosan is pH- and thermo- responsive in hydrogel formation.•The modified polysaccharide did not show any cytotoxicity. The present contribution deals with the synthesis and characterization of N-isopropyl chitosan in which the introduction of hydrophobic groups leads to an increased flexibility of the polysaccharide backbone. The isopropyl groups extend the solubility of the modified-chitosan samples and render the modified chitosan a pH- and thermo-sensitive system for hydrogel formation. Indeed, upon varying the pH of the system and/or its temperature within a range compatible with biological applications, a non-reversible sol-gel transition occurs, as determined through extended rheological analyses. The modified chitosan samples show a very good biocompatibility as determined through preliminary viability and cell growth experiments.